Journal of Oleo Science Copyright ©2020 by Japan Oil Chemists’ Society doi : 10.5650/jos.ess19239 J. Oleo Sci. 69, (7) 693-701 (2020) Synthesis of Sucrose Fatty Acid Esters by Using Mixed Carboxylic-fatty Anhydrides Iteb Trabelsi, Kamel Essid＊ , and Mohamed Hedi Frikha Laboratory of Organic Chemistry LR17ES08: Faculty of sciences in Sfax, Route de Soukra Km 3,5 – BP 1171-3000. Sfax. TUNISIA Abstract: Fatty acid sugar esters are non-ionic surfactant active agents with excellent performance and many uses. This work is devoted to the synthesis of sugar esters by the esterification reaction of sugar with mixed carboxylicpalmitic anhydrides using resin Amberlyst-15 as heterogeneous acid catalyst. These anhydrides should be stable and react as acylating agents. Influence of different reaction parameters, such as the molar ratio (sucrose/anhydride), the type of solvent and the reaction time on the yield of the esterification reaction were studied. The esterification reaction of sucrose with mixed palmitic benzoic anhydride leads to a mixture of sucrose esters of palmitic acid with a good percentage of conversion. The mixed anhydride was both reactive and selective for the preparation of fatty acid ester. Key words: fatty acid, mixed anhydride, heterogeneous acid catalyst, resin Amberlyst-15, esterification, sucrose, acylation of sucrose, sucrose fatty acid esters (SEs) 1 Introduction mixed anhydrides have been often employed in order to Sucrose fatty acid esters（SEs）, commonly called sugar obtain a high yield of ester16）. Mixed anhydrides obtained esters, are nonionic surfactants that have excellent emulsi- from two different carboxylic acids are molecules finding fying, stabilizing, detergency and other useful effect1－4）. an increasing interest in the chemical industry due to their Sugar esters are attractive because of their ready biode- high reactivity17, 18）. gradability, low toxicity and low irritation to eyes and skin5－7）. The objective in this work is to develop new techniques They have a large number of applications in industry such for the synthesis of sugar fatty acid esters by chemical as the pharmaceutical, cosmetic, detergent and food8－10）. means allowing the production of economic compounds In addition, their antimicrobial, antitumoral and insecticidal （raw materials and manufacturing processes）and environ- properties have been reported and might open new mentally friendly. markets7, 11）. The sucrose esters（SEs）are consisted from This work is devoted to the development of new reaction natural raw materials: sucrose as hydrophilic group and pathways for obtaining a sucrose fatty acid ester using fatty acids as lipophilic groups12）. Sucrose has eight hy- mixed carboxylic-fatty anhydride in the presence of ion ex- droxyl groups, which allow the formation of esters from change resins（Amberlyst-A15）as a catalyst. monoesters to octaesters with different fatty acid8, 12, 13）Su- croesters can be synthesized either by using chemical or enzymatic processes1, 2）. The chemical process is generally performed at high temperature in toxic solvents which 2 Experimental leave traces in the products, which is accompanied by low 2.1 Synthesis of sucrose octaacetate selectivity toward the various hydroxyl groups in sugars 2.1.1 Acylation reaction of sucrose solvent-free and forming coloured derivatives as side-products1－4, 11, 14, 15）. 5 g（0.014 mol）of sucrose, 100 mL（1.055 mol）of acetic Product of chemical synthesis is often an undefined and anhydride used as reactant and solvent in the reaction and complex mixture of mono-, di- and poly-esters, which is 2 g（9.4 meq/g）of resin Amberlyst A-15 as catalyst were difficult to be characterized with respect to its physical charged in a 250 ml flask. The reaction mixture was stirred properties and surfactive1, 2, 14）. Sugar esters are synthe- for 6 hours in oil bath at 50-55℃. sized by esterfication of sugars or sugar alcohols with fatty When the reaction was completed, the reaction mixture acids1）. Because the esterification is a reversible reaction, was filtered and the Amberlyst-15 washed 3 times with ＊Correspondence to: Kamel Essid, Laboratory of Organic Chemistry LR17ES08: Faculty of sciences in Sfax, Route de Soukra Km 3,5 – BP 1171-3000. Sfax. TUNISIA E-mail: [email protected] Accepted March 26, 2020 (received for review September 22, 2019) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/ http://mc.manusriptcentral.com/jjocs 693 I. Trabelsi, K. Essid, and M. H. Frikha acetic anhydride（10 mL）. The organic phase was slowly 3 Results and Discussion added to 600 mL of a mixture（water/ice）then allowed to In a previous work, we have studied the synthesis of stand for 12 hours. The syrup formed in this period was fatty esters by the esterification with mixed carboxylic pal- separated from the aqueous phase. The aqueous phase was mitic anhydrides. These anhydrides characterized by the extracted 3 times with 30 mL of chloroform. The chloro- general formula C15H31COOCOR can be easily prepared by form extracts were combined, evaporated in vacuo and the reaction of palmitic acid with aliphatic or aromatic acid added to the syrup. The mixture obtained was then dis- chloride in the presence of triethylamine and in organic solved in 30 mL of ethanol. A small volume of water（～10 solvent19）. The esterification reaction of primary, secondary mL）was added dropwise until the solution becomes turbid. and tertiary alcohols with mixed aliphatic palmitic anhy- Crystallization of the final product was carried out at 5℃ dride and mixed aromatic palmitic anhydride was realized and white crystals were obtained. The products recrystal- in the presence of resin Amberlyst-15 as heterogeneous lized were weighed and analyzed by IR and（1H and 13C） acid catalyst. We have showed that the palmitic group of NMR spectroscopy. The yield of the acylation reaction was the mixed carboxylic palmitic anhydride was the most in- determined by calculating the ratio between the mass of volved in the esterification reaction and the leaving of the sucrose octaacetate（after recrystallization）and the theo- alkyl or aryl group of the mixed anhydride. The preferential retical mass of ester formed. esterification of alcohol was realized by the palmitic group 2.1.2 Acylation reaction of sucrose in solvent of mixed carboxylic palmitic anhydride and the obtained 5 （g 0.014 mol）of sucrose, 20 mL（0.527 mol）of acetic an- palmitic esters were produced with good yields. We have hydride and 2 （g 9.4 meq/g）of resin Amberlyst A-15 as cata- found that the mixed aliphatic palmitic anhydrides were lyst were added in a 250 mL flask. The reactants were less reactive and less selective than their mixed aromatic placed in an organic solvent such as dichloromethane, palmitic anhydrides19, 20）. Among tested mixed aromatic diethyl ether, hexane and chloroform. The mixture was palmitic anhydrides, we have chosen the mixed benzoic then stirred under refluxing of the solvent. At the end of palmitic anhydride in the esterification reaction of sucrose the reaction, the mixture reaction obtained was treated in using resin Amberlyst-15 as heterogeneous acid catalyst. the same manner as before until a dry product was ob- tained. The products recrystallized were weighed and ana- 3.1 Synthesis of sucrose octaacetate lyzed by IR and（1H and 13C）NMR spectroscopy. The yield We have taken first, as a simple model of anhydride: of the acylation reaction was determined by calculating the acetic anhydride in the acylation reaction of sucrose in the ratio between the mass of sucrose octaacetate（after re- presence of a catalyst. We have studied the influence of the crystallization）and the theoretical mass of ester formed. main experimental parameters such as the molar ratio （sucrose/acetic anhydride）and the type of solvent on the 2.2 Synthesis of sucroesters by mixed benzoic-palmitic yield of the acylation reaction. anhydride 3.1.1 Effect of type of solvent 3 g（8.33 10－3 mol）of crude mixed benzoic palmitic an- We have studied the effect of type of solvent on the yield hydride, 2 g, 0.5 g then 0.3 g of sucrose corresponding re- of sucroesters. The acylation reaction involves the ex- spectively to the molar ratios（sucrose/anhydride）（ 1:1.5）, change of the（OH）group of the sucrose by the（OCOCH3） （1:6）and（1:10）and 2 g（9.4 meq/g）of Amberlyst-15 are group of the acetic anhydride in the presence of an ion ex- were stirred under reflux of organic solvent such as hexane change resin Amberlyst-15 as heterogeneous catalyst. The and cyclohexane. After completion of the reaction, the re- reaction mixture was stirred for 6 hours at a temperature action mixture was filtered and the Amberlyst-15 resin was of 50-55℃（ without solvent）or under reflux of solvent as washed with the organic solvent（20 mL）. The solvent was indicated in Scheme 1. then evaporated to dryness and the crude product was The acylation reaction was carried out with a large weighed and analyzed by IR, 1H NMR and 13C NMR. excess of acetic anhydride used as reactant and solvent. Then, we introduced an organic solvent in the reaction 2.3 Spectroscopic analysis medium to facilitate the contact between the reactants and The FT-IR spectra of the crude products were recorded to ensure the better reactivity. Solvents of different polari- on a spectrometer type Perkin Elmer Spectrum version 10. ties were used while keeping the same procedure. The The NMR spectra of the crude products were recorded yields of recrystallized products were resumed in the Table in solution in CDCl3 on a spectrometer type Bruker Avance 1 and the structure of these products was confirmed by IR III HD（1H at 400 MHz and 13C at 100 MHz）.